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Mash temperatures

In the mash, grain is heated to one of a series of temperatures in order to complete different chemical and enzymatic changes in the wort.

The chart below lists some of the common mash temperatures or rests used by homebrewers. For more information about a particular rest, see the links in the chart or the description of mashing at the Mashing page.

Temp. (C)

Temp. (F)

Name

Effects

35-45

95-113

Doughing-In

Allows the mash to absorb water and distributes enzymes throughout the mash. These temperatures will also result in some acid rest activity, potentially changing the pH of the mash.

30-52 (35)

85-125 (95)

Acid rest

Rarely needed for home brewers. An acid rest activates the enzyme phytase, lowering the pH of the mash. This rest was used to lower the pH in traditional Pilsner brewing where soft water and pale malts were used.

up to 50

104-120

Beta-glucan rest

Break down beta-glucanases in unmalted barley and wheat, rolled oats, and other unmalted or undermodified grains. Without a low-temperature rest, beta-glucans will result in a gummy mash.

45-55

113-130

Protein rest

Activates protease and peptase enzymes, which break down the large, insoluble proteins in the mash into smaller, soluble proteins and amino acids. These temperatures will also result in some acid rest activity, potentially changing the pH of the mash.

Saccharification rest

The one rest necessary in every mash; at these temperatures, alpha-amylase, beta-amylase, and limit-dextrinase, among other enzymes, break down the large starches into sugars, including fermentable sugars. The specific temperatures at which these enzyme

C

F

Enzyme

Role

60-67

140-153

Limit dextrinase

Degrades large starches into smaller starches accessible to alpha-amylase

60-75

140-167

Alpha amylase

Breaks down starches into sugars, including some fermentable sugars and some unfermentable sugars

60-65

140-150

Beta-amylase

Breaks down complex sugars into simpler fermentable sugars

Note that the most common mash temperatures, between 153 and 155 degrees F, are actually above the temperature where beta amylase is denatured. However, as it denatures, it does still operate in the wort, allowing a single-step infusion rest.

Because these enzymes operate at different temperatures, by adjusting the temperature to favor one enzyme over another the brewer can adjust the fermentability of the sugars in the wort.